An indoor positioning system (IPS) is a network of devices used to locate people or objects where GPS and other satellite technologies lack precision or fail entirely, such as inside multistory buildings, airports, alleys, parking garages, and underground locations.Magda Chelly, Nel Samama. New techniques for indoor positioning, combining deterministic and estimation methods. ENC-GNSS 2009 : European Navigation Conference - Global Navigation Satellite Systems, May 2009, Naples, Italy. pp.1 - 12. ⟨hal-01367483⟩
A large variety of techniques and devices are used to provide indoor positioning ranging from reconfigured devices already deployed such as smartphones, Wi-Fi and Bluetooth antennas, digital cameras, and clocks; to purpose built installations with relays and beacons strategically placed throughout a defined space. Lights, radio waves, magnetic fields, acoustic signals, and behavioral analytics are all used in IPS networks. IPS can achieve position accuracy of 2 cm, which is on par with RTK enabled GNSS receivers that can achieve 2 cm accuracy outdoors. IPS use different technologies, including distance measurement to nearby anchor nodes (nodes with known fixed positions, e.g. Wi-Fi / Li-Fi access points, Bluetooth beacons or Ultra-Wideband beacons), magnetic positioning, dead reckoning. They either actively locate mobile devices and tags or provide ambient location or environmental context for devices to get sensed.THES, Propagation of a position in a connected network, Chelly, Magda Lilia; Samama, Nel; 2011, 2011TELE0018, The localized nature of an IPS has resulted in design fragmentation, with systems making use of various optical,Liu X, Makino H, Mase K. 2010. Improved indoor location estimation using fluorescent light communication system with a nine-channel receiver. IEICE Transactions on Communications E93-B(11):2936-44. radio, or even acoustic technologies.
IPS has broad applications in commercial, military, retail, and inventory tracking industries. There are several commercial systems on the market, but no standards for an IPS system. Instead each installation is tailored to spatial dimensions, building materials, accuracy needs, and budget constraints.
For smoothing to compensate for stochastic (unpredictable) errors there must be a sound method for reducing the error budget significantly. The system might include information from other systems to cope for physical ambiguity and to enable error compensation. Detecting the device's orientation (often referred to as the compass direction in order to disambiguate it from smartphone vertical orientation) can be achieved either by detecting landmarks inside images taken in real time, or by using trilateration with beacons.Positioning and orientation using image processing a 2007 research from the University of Washington. Several similar approaches have been developed and there are currently (2017) smartphone applications implementing this technology. There also exist technologies for detecting magnetometric information inside buildings or locations with steel structures or in iron ore mines.Startup uses a smartphone to track people indoors, - About Indoor Atlass (MIT Technology Review website)
Applicability and precision
Due to the signal attenuation caused by construction materials, the satellite based Global Positioning System (GPS) loses significant power indoors affecting the required coverage for receivers by at least four satellites. In addition, the multiple reflections at surfaces cause multi-path propagation serving for uncontrollable errors. These very same effects are degrading all known solutions for indoor locating which uses electromagnetic waves from indoor transmitters to indoor receivers. A bundle of physical and mathematical methods is applied to compensate for these problems. Promising direction radio frequency positioning error correction opened by the use of alternative sources of navigational information, such as inertial measurement unit (IMU), monocular camera Simultaneous localization and mapping (SLAM) and Wi-Fi SLAM. Integration of data from various navigation systems with different physical principles can increase the accuracy and robustness of the overall solution.Vladimir Maximov and Oleg Tabarovsky, LLC RTLS, Moscow, Russia (2013). Survey of Accuracy Improvement Approaches for Tightly Coupled ToA/IMU Personal Indoor Navigation System. Proceedings of International Conference on Indoor Positioning and Indoor Navigation, October 2013, Montbeliard, France.See publication here
Indoor Positioning Systems are highly effective in environments where GPS signals are weak or unavailable, such as hospitals, malls, warehouses, factories, airports, and underground facilities. The achievable accuracy depends on the technology used. Wi-Fi and Bluetooth-based systems typically provide accuracy between 1–5 meters, making them suitable for navigation and asset tracking, while advanced technologies like UWB (Ultra-Wideband) can achieve centimeter-level precision for high-accuracy applications such as robotics, industrial automation, and real-time equipment tracking. However, factors like wall materials, signal interference, multipath reflections, and moving objects can impact performance and reduce positioning accuracy.
The U.S. Global Positioning System (GPS) and other similar global navigation satellite systems (GNSS) are generally not suitable to establish indoor locations, since microwaves will be attenuated and scattered by roofs, walls and other objects. However, in order to make the positioning signals become ubiquitous, integration between GPS and indoor positioning can be made.Wan Mohd Yaakob Wan Bejuri, Mohd Murtadha Mohamad and Raja Zahilah (2015). Offline Beacon Selection-Based RSSI Fingerprinting for Location-Aware Shopping Assistance: A Preliminary Result. New Trends in Intelligent Information and Database Systems, pp. 303-312, See publication hereWan Mohd Yaakob Wan Bejuri, Mohd Murtadha Mohamad and Raja Zahilah (2015). Emergency Rescue Localization (ERL) using GPS, Wireless LAN and Camera" International Journal of Software Engineering and Its Applications, Vol. 9, No. 9, pp. 217-232, https://serscjournals.org/index.php/IJSEIA/vol9_no9_2015/19.pdfWan Mohd Yaakob Wan Bejuri and Mohd Murtadha Mohamad (2014). Performance Analysis of Grey-World-based Feature Detection and Matching for Mobile Positioning Systems. Sensing and Imaging, Vol. 15, No. 1, pp. 1-24 Wan Mohd Yaakob Wan Bejuri, Wan Mohd Nasri Wan Muhamad Saidin, Mohd Murtadha Mohamad, Maimunah Sapri and Kah Seng Lim (2013). Ubiquitous Positioning: Integrated GPS/Wireless LAN Positioning for Wheelchair Navigation System. Intelligent Information and Database Systems, Vol. 7802, pp. 394-403, See publication hereWan Mohd Yaakob Wan Bejuri, Mohd Murtadha Mohamad, Maimunah Sapri and Mohd Adly Rosly (2012). Ubiquitous WLAN/Camera Positioning using Inverse Intensity Chromaticity Space-based Feature Detection and Matching: A Preliminary Result. International Conference on Man-Machine Systems 2012 (ICOMMS 2012). See publication hereZ. Horvath, H. Horvath (2014): The Measurement Preciseness of the GPS Built in Smartphones and Tablets, International Journal on Electronics and Communication Technology, issue 1, pp 17-19,
Currently, GNSS receivers are becoming more and more sensitive due to increasing microchip processing power. High sensitivity GNSS receivers are able to receive satellite signals in most indoor environments and attempts to determine the 3D position indoors have been successful. Besides increasing the sensitivity of the receivers, the technique of A-GPS is used, where the almanac and other information are transferred through a mobile phone.
However, despite the fact that proper coverage for the required four satellites to locate a receiver is not achieved with all current designs (2008–11) for indoor operations, GPS emulation has been deployed successfully in Stockholm metro. GPS coverage extension solutions have been able to provide zone-based positioning indoors, accessible with standard GPS chipsets like the ones used in smartphones.
Types of usage Locating and positioning While most current IPS are able to detect the location of an object, they are so coarse that they cannot be used to detect the orientation or direction of an object.
Locating and tracking
One of the methods to thrive for sufficient operational suitability is "tracking". Whether a sequence of locations determined form a trajectory from the first to the most actual location. Statistical methods then serve for smoothing the locations determined in a track resembling the physical capabilities of the object to move. This smoothing must be applied, when a target moves and also for a resident target, to compensate erratic measures. Otherwise the single resident location or even the followed trajectory would compose of an itinerant sequence of jumps.
Identification and segregation In most applications the population of targets is larger than just one. Hence the IPS must serve a proper specific identification for each observed target and must be capable to segregate and separate the targets individually within the group. An IPS must be able to identify the entities being tracked, despite the "non-interesting" neighbors. Depending on the design, either a sensor network must know from which tag it has received information, or a locating device must be able to identify the targets directly.
Wireless technologies
Any wireless technology can be used for locating. Many different systems take advantage of existing wireless infrastructure for indoor positioning. There are three primary system topology options for hardware and software configuration, network-based, terminal-based, and terminal-assisted. Positioning accuracy can be increased at the expense of wireless infrastructure equipment and installations.
Wi-Fi-based positioning system (WPS)
Wi-Fi positioning system (WPS) is used where GPS is inadequate. The localization technique used for positioning with wireless access points is based on measuring the intensity of the received signal (received signal strength in English RSS) and the method of "fingerprinting".P. Bahl and V. N. Padmanabhan, "RADAR: an in-building RF-based user location and tracking system," in Proceedings of 19th Annual Joint Conference of the IEEE Computer and Communications Societies (INFOCOM '00), vol. 2, pp. 775–784, Tel Aviv.Israel, March 2000.Y. Chen and H. Kobayashi, "Signal strength based indoor geolocation," in Proceedings of the IEEE International Conference on Communications (ICC '02), vol. 1, pp. 436–439, New York, NY, USA, April–May 2002. To increase the accuracy of fingerprinting methods, statistical post-processing techniques (like Gaussian process theory) can be applied, to transform discrete set of "fingerprints" to a continuous distribution of RSSI of each access point over entire location.Golovan A. A. et al. Efficient localization using different mean offset models in Gaussian processes //2014 International Conference on Indoor Positioning and Indoor Navigation (IPIN). – IEEE, 2014. – С. 365-374.Hähnel B. F. D., Fox D. Gaussian processes for signal strength-based location estimation //Proceeding of robotics: science and systems. – 2006.Ferris B., Fox D., Lawrence N. D. Wifi-slam using gaussian process latent variable models //IJCAI. – 2007. – Т. 7. – №. 1. – С. 2480-2485. Typical parameters useful to geolocate the Wi-Fi hotspot or wireless access point include the SSID and the MAC address of the access point. The accuracy depends on the number of positions that have been entered into the database. The possible signal fluctuations that may occur can increase errors and inaccuracies in the path of the user. (Best Demo Award)
Bluetooth
Originally, Bluetooth was concerned about proximity, not about exact location.